If you are interested in a tour, you should try for early Friday morning, 'cause some of the guides will be tied up with the relic show the rest of the weekend, & it's good to have the tour at the beginning of your visit so you can return to the spots that interest you.
Here's my guide to first timers -
Bone up on the battle before you go. Seeing certain areas – Devil’s Den, The Wheatfield, Little Round Top, Culp’s Hill, the railroad cut, the Pickett - Pettigrew - Trimble Charge, etc. – will mean a lot more to you if you know what happened there before you see them for the first time. National Geographic put out a good map, showing the armies’ approaches towards Gettysburg, in 2013.
Read the Gettysburg chapter in
I Rode with Stonewall by Henry Kyd Douglas, & chapter 11 of
Fighting for the Confederacy by Edward Porter Alexander. There are plenty of books that can tell you more - I enjoyed (most of)
Gettysburg: The Last Invasion by Allen C. Guelzo. Watch the movie Gettysburg – after reading about the battle. (You might enjoy the easy to read historical novel
The Killer Angels – adapted by the movie Gettysburg – which won the 1975 Pulitzer prize for fiction.)
Take a car tour (the guide drives your car) – all sorts of tours are available, but you’ll probably want the general tour if you’ve never been before – it takes about two hours – and then go back to walk the areas you read about & your guide talked about. If you are interested in a tour, I suggest you set it up days in advance. Call the Visitor’s Center & ask how to do this. Some guides are better than others, and you can request them by name. The new Visitor’s Center was disappointing to me. It tries to tell a politically correct version of the war, & the lead up to the war, and the entire war, rather than focusing on the battle & showing the many relics that it has locked away in storage. The display portions used to be free – but not any more! (However, there is a big food court, & a souvenir shop the size of a football field.)
Definitely walk the path of the Pickett - Pettigrew - Trimble Charge (from Seminary Ridge to Cemetery Ridge, & back again). I suggest you do that at the end of your visit. There are two paths cut through the fields in the summer. Keep an eye out (and wear repellent) for ticks during the warm months.
Visit The Horse Soldier (219 Steinwehr Avenue) & Union Drummer Boy (37 York Street) – they are high end relic shops, & they have more relics on display than you’ll see at the Visitor’s Center.
The Farnsworth House is a good place to eat lunch (401 Baltimore Street). Two neat places to grab a beer or drink at night are the Reliance Mine Saloon (in the NE corner of the Quality Inn @ 380 Steinwehr Ave. parking lot – it’s hard to find, but unique) & the basement bar @ the Dobbin House (89 Steinwehr Ave.). Several years ago I discovered the upstairs bar at The Garyowen Irish Pub (126 Chambersburg Street), and I’ve drunk many a Red Breast there ever since.
Call the Visitor’s Center, go on line, or see if your motel has literature about any demonstrations taking place. Reenactors often camp at Pitzer Woods & Spangler’s Spring, & put on artillery firing, rifle firing, camp life, etc. demos. two or three times a day on Sats. & Suns. (but this slows down in the cold months). Climb the towers on Culp’s Hill and at the southern end of Confederate Avenue.
Pick up a National Park Service map as early in your trip as you can – it’s helpful in seeing where all the battlefield sites are, & could save you time & keep you from getting lost.
Here’s an interesting (to me, you have to be dedicated to read it all) link to a study on the Devil’s Den sniper
http://www.jamescgroves.com/henry/hcp1a.htm The official position of the Park Service is that the body was found elsewhere, photographed at that site, drug to Devil’s Den, and photographed again. The park rangers I know agree with the conclusions of the link’s author – the body was originally found in Devil’s Den, is that of the sniper, was photographed, drug down the hill, and photographed again.
There are two relic shows each year in (or near) Gettysburg. One is the last weekend in June, the other is in the fall. You have to pay an entrance fee, but there are lots of relics on display.